1. Field of the Invention
The present invention relates to a traveller changer for automatically changing a traveller fitted on a ring of a ring spinning frame. Particularly, the invention is concerned with a traveller changer in which a tensor for absorbing the slack of yarn which has been slackened for traveller change is sure to operate.
2. Prior Art
A ring spinning frame using a traveller will first be described with reference to FIG. 19. A ring spinning frame 101 has a twisting mechanism 102 and a drafting mechanism 103. The drafting mechanism 103 comprises a pair of upper and lower back rollers 104, a pair of upper and lower middle rollers 106 each having an apron 105, and a pair of upper and lower front rollers 107, arranged successively from above to below. The upper roller of each roller pair is supported so as to permit opening and closing by means of a cradle arm, while the lower roller of each roller pair is driven. A sliver or roving S of a large diameter passes through the drafting mechanism 103 into yarn. The yarn then passes through the twisting mechanism 102 about to be described, into spun yarn. The twisting mechanism 102 comprises a spindle 1 onto which is fitted a bobbin 2, a ring rail 4 capable of traversing and movable vertically in the longitudinal direction of the bobbin 2, a ring 5 fixed to the ring rail 4, a traveller 7 fitted on a flange 6 of the ring 5 and capable of travelling in the circumferential direction, a ballooning control ring 9 and a snail wire 8, these components being arranged successively from below to above. The spindle 1 is allowed to rotate at a high speed of usually 10,000 to 20,000 r.p.m. by means of a belt 3 which is common to plural spindles. Yarn Y is wound onto the bobbin 2 through the snail wire 8, ballooning control ring 9 and further through the traveller 7. As the bobbin 2 rotates, the traveller 7 is pulled by the yarn and travels on the flange 6 of the ring 5, thereby twisting the yarn. Between the bobbin 2 and the traveller 7 there is a difference in the number of revolutions which corresponds to the length of yarn fed from above. The yarn is wound by this length onto the bobbin 2. Thus, the ring 5 and the traveller 7 serves not only as a frictional resistor for inducing a difference in the number of revolutions but also as a travelling direction changing mechanism for performing both twisting and winding operations.
The traveller 7 is a C-shaped metallic piece and is fitted on the flange 6 of the ring 5. Since the traveller 7 rotates on the flange 6 at a high speed of 10,000 to 20,000 r.p.m., it wears out, and hence every week or two it is necessary to change the traveller 7 from old to new one. The conventional traveller changing method is a manual method. More particularly, an old traveller is removed using a suitable pawl piece, and then a new traveller is mounted, using a traveller mounting device as a manual tool where required.
Since the conventional traveller changing method is a manual method although it uses a tool, if all the travellers in a ring spinning frame having a large number of spindles are to be changed, a considerable time is required even for a skilled worker. Thus, a special worker for the change of travellers is required.
Because of such inconvenience, an automatic traveller changer has come to be desired. For automatic change of a traveller, a bobbin is rotated reversely to slacken the yarn passed on the traveller. The slack of the yarn is absorbed by a tensor. Then, the bobbin is rotated forward, allowing the traveller to travel until it is hooked by a traveller removing device. The yarn is shifted onto a ring by means of a yarn hooking lever. A new traveller is mounted and thereafter the old traveller is removed. The slacken yarn is tensed by rotating the bobbin forward. Thus, many operations are required and it is necessary to perform these operations efficiently.
The ring rail 4 in FIG. 10 moves up and down in a section L and in which position in the section L it is to stop is indefinite. However, the yarn which is absorbed its slack by the tensor is located in a higher position than the snail wire 8, which position is not influenced by the vertical movement of the ring rail 4. In the case where a tensor and a traveller changer are provided integrally with each other, therefore, there is a fear of the tensor operation becoming uncertain because of a positional change of yarn absorbed by the tensor.